1. Field of the Invention
The present invention provides a method of preparing furfural compounds from aldohexose-containing substrate.
2. Description of the Related Art
5-hydroxymethyl-2-furfural (5-HMF), a purine compound that may be derived from renewable biomass, is an intermediate in the production of industrially-important materials. 5-HMF can be converted to 2,5-dimethylfuran (DMF) for liquid biological fuel, and oxidized to 2,5-furandicarboxylic acid (FDCA) for polyester production. Recently, FDCA has been in the limelight as a substituent for terephthalate. In addition, 5-HMF can be converted to an environment-friendly adhesive, cohesive, and coating agent. Thus, there are several studies being done on the mass production of 5-HMF.
The conventional method of producing 5-HMF has used fructose. The fructose of ketohexose can be converted to HMF using only dehydration in the presence of acid catalyst, without requiring an additional isomerization. However, fructose is expensive, and the high boiling point of the solvent used in the conversion requires high energy distillation to be removed. Thus, the 5-HMF production method using fructose has good availability, but cannot be used widely because of its high production cost.
5-HMF can be prepared by thermal dehydration from hexose substrate in the presence of various catalysts in the acidic solution. In this regard, there has been an attempt to develop a chemical synthetic process having a low cost and high yield.
In the disclosure of EP2183236B1, 5-hydroxymethylfurfural was obtained from hexose using an ionic liquid containing an organic cation and an inorganic anion. However, the ionic liquid as a reactant solvent has too a high viscosity to be used in a commercially available process, limited by mass transfer and workability. In addition, impurities in the ionic liquid process has an undesirable effect on the catalytic reaction, and causes some problems in the separation of the reactants and the products.
WO 09/155297 discloses that glucoses is converted to 5-HMF at 81% yield in a polar aprotic solvent. However, the use of organic solvent makes it hard to separate the produced 5-HMF, and thus, the method is difficult to commercialized.
In the prior art, 5-HMF was produced from fructose at a high yield, but from glucose at a very low yield. There is a process of preparing 5-HMF from glucose using various solvents to improve the yield of production from glucose, but it is very complicated process and has a high production cost.
The catalysts used for producing 5-HMP are inorganic acids such as H2SO4, H3PO4 and HCl, which are hard to regenerate due to the use of solution. In order to address the regeneration problem, solid sulfuric acid is often used as a catalyst. Because an inactive humin polymer is produced on the surface of a solid acid resin, the solid acid resin is used restrictively.
Therefore, there is a need for a method of efficiently preparing 5-HMF and its derivatives from inexpensive feedstock.